In the commonly owned German patent document DE-OS 33 01 688 (corresponding to U.S. Pat. No. 4,539,024), an apparatus of the general type to which the invention is directed, has been described.
In this system, the flue gas inlet is provided at the bottom of the generally cylindrical scrubbing column and a flue gas outlet is provided at the head of this column which is of round cross section. Means is provided within the column for feeding the scrubbing liquid into the flue gas rising in the column and the column has a scrubbing liquid sump in which a suspension of calcium sulfite and/or calcium sulfate is collected or is formed. The suspension can be withdrawn from the sump and the head of the scrubbing column has a water separator for stripping liquid, entrained by the flue gas to the head, from the flue gas before it leaves the apparatus.
The flue gas outlet is connected generally radially with the head of the scrubbing column and the water separator comprises a number of water separator registers, i.e. arrays of impingement baffle separator plates or surfaces.
In the construction of this patent document, the water separator forms a crown of water separator registers, each of which comprises a plurality of spaced-apart impingement baffle units surrounding a flue gas inlet region in the center of the crown or array. The registers are located in sectors and are traversed in a radial direction by the flue gas.
Surrounding the crown of liquid separators, is an annular outlet channel for the flue gas and the flow cross section of this channel can progressively increase in the direction of the radial flue gas outlet from a location diametrically opposite this outlet.
In an improvement upon that system described in German Patent Document DE-OS 34 10 110 (U.S. Pat. No. 4,626,264), the annular outlet channel is divided over its periphery by at least two control elements (valve flaps, dampers, or plates) controlled by a servo-mechanism or other effector which can close off the flow cross section so that parts of the outlet channel can be blocked during partial load operations.
The water separation registers can then be caused to function as preseparator and main-separator units as desired.
This system requires a generally circular construction of the head and a generally circular flow of the gas. This construction and gas flow pattern has not proved to be the most effective or desirable in many cases.